linux-kernel - [PATCH 1/6] dt-bindings: media: video-interfaces: add support for Virtual Channel IDs

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Message-ID: <20250220141739.228714-2-demonsingur@gmail.com>
Date: Thu, 20 Feb 2025 16:17:23 +0200
From: Cosmin Tanislav <demonsingur@...il.com>
To: 
Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-media@...r.kernel.org,
	devicetree@...r.kernel.org,
	imx@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Cosmin Tanislav <demonsingur@...il.com>
Subject: [PATCH 1/6] dt-bindings: media: video-interfaces: add support for Virtual Channel IDs

Multi-camera systems often have issues with receiving video streams
from multiple cameras at the same time because the cameras use the same
Virtual Channel IDs.

CSI bridges might not support remapping the Virtual Channel IDs, making
it impossible to receive the separate video streams at the same
time, while the CSI receiver is able to de-mux streams based on VC IDs.

Cameras sometimes have support for changing the VC IDs they output
themselves.

For a practical example, GMSL2 deserializer chips do not support VC ID
remapping in tunnel mode, and neither do the serializers. Allowing the
cameras to have their VC IDs configured would allow multi-camera setups
to use tunnel mode.

Add support for specifying these Virtual Channel IDs in Video Interface
Endpoints. The supported values are 0 to 3, with a maximum of 4 values.
Although the CSI-2 specification allows for up to 32 virtual channels,
most hardware doesn't support more than 4. This can be extended later
if need be.

Signed-off-by: Cosmin Tanislav <demonsingur@...il.com>
---
 .../devicetree/bindings/media/video-interfaces.yaml   | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/media/video-interfaces.yaml b/Documentation/devicetree/bindings/media/video-interfaces.yaml
index 038e85b45befa..414b5fa8f3472 100644
--- a/Documentation/devicetree/bindings/media/video-interfaces.yaml
+++ b/Documentation/devicetree/bindings/media/video-interfaces.yaml
@@ -231,6 +231,17 @@ properties:
       shall be interpreted as 0 (ABC). This property is valid for CSI-2 C-PHY
       busses only.

+  vc-ids:
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+    minItems: 1
+    maxItems: 4
+    items:
+      maximum: 3
+    description:
+      An array of Virtual Channel IDs. These are unsigned integers that specify
+      the VC IDs used by the device for its data streams. This property is valid
+      for MIPI CSI-2 only.
+
   strobe:
     $ref: /schemas/types.yaml#/definitions/uint32
     enum: [ 0, 1 ]
-- 
2.48.1